Ethernet network technology not only has been widely applied in local area network environments of enterprises, but also interests telecommunication providers increasingly in building provider Ethernet networks, due to its advantages such as low cost, mature standard and flexible techniques. An important reason among others is that the Ethernet network technology has advantages such as low cost and statistical multiplexing function. However, due to limitations of conventional Ethernet network techniques, such as poor extensibility and interoperability, a series of problems occur when extending an Ethernet network application to a metropolitan area network.
In order to solve the extensibility of the Ethernet network, those skilled in the art proposed a technical scheme called MAC-in-MAC (Media Access Control). In the MAC-in-MAC technical scheme, when a data packet of a client arrives at a Provider Edge Bridge (PEB), the PEB encapsulates the data packet with an outer MAC header, a source address of which is a MAC address of the present PEB and a destination address of which is a MAC address of a destination PEB. To encapsulate with the outer MAC header, it is necessary for the PEB to perform address learning according to the source address of the outer MAC header of the received data packet to obtain mapping between a destination address of the client and the address of the destination PEB. The MAC-in-MAC technical scheme enables an internal bridge in a provider network to mask the MAC address of a network of the client.
On the basis of the MAC-in-MAC technical scheme, IEEE has established a new standard 802.1ah, and an 802.1ah-based network is referred to as a Provider Backbone Bridged Network (PBBN). However, the standard 802.1ah is under refinement, and there is no mature solution for forwarding data in a multi-PBBN environment yet.
At present, there exist two technical schemes on the basis of tiered interconnection and peer-to-peer interconnection in the conventional art for solving the data forwarding in the multi-PBBN environment. Hereunder, the two technical schemes will be further described in detail with reference to the accompanying drawings.
In a tiered interconnection model, a plurality of PBBNs are divided into several levels. The PBBN on an upper level serve as a service level for a PBBN on a lower level to provide a transparent transmission service for data transmission between the PBBNs on the lower levels.
With reference to FIG. 1, a Provider Bridged Network (PBN) on a lowest level is a provider network constructed on the basis of a Q-in-Q scheme in IEEE 802.1ad, and is adapted to provide an Ethernet network service for a client bridged network. The Q-in-Q scheme extends the Ethernet network and achieves isolation between a provider VLAN and a client VLAN. A typical message format in the PBN is as follows.
C-DAC-SAS-TAGC-TAGClient-DataFCSWhere the C-DA is the destination address of a client, namely, the Destination Address (DA) of data packets of the client; the C-SA is the source address of the client, namely, the Source Destination (SA) of the data packets of the client; the S-TAG is TAG of a VLAN in the PBN; the C-TAG is TAG of the VLAN carried in the data packets of the client; and the FCS is a frame check sequence.
The three PBBNs on the upper levels are a provider backbone Ethernet network constructed on the basis of the MAC-in-MAC scheme in the IEEE 802.1ah, and are mainly adapted to interconnect a plurality of the PBNs. A typical message format in the PBBN is as follows.
B-DAB-SAB-TAGI-TAGClient-DataFCSWhere the B-DA (Provider Backbone Destination Address) is the destination address of the provider backbone bridge, namely, the destination address for the outer MAC header; the B-SA (Provider Backbone Source Address) is the source address of the provider backbone bridge, namely, the source address for the outer MAC header; the B-TAG (Backbone VLAN TAG) is a tag of the backbone VLAN; the I-TAG (Service Instance TAG) is a tag of a service instance; and Client-Data here is a data packet of a complete format in the PBN.
According to planning, the three PBBNs can be divided into two levels of Level 1 and Level 2 by the provider. A plurality of PBBNs on Level 1 are connected by the PBBN on Level 2. Data is transmitted between the two PBBNs on Level 1 through the transparent transmission of the PBBN on Level 2. The PBBN on Level 2 treats a data packet from Level 1 at an ingress node as a payload. The data packet from Level 1 is encapsulated with the outer MAC header for the present level, and an Ethernet network data packet encapsulated is forwarded on the present level in accordance with the outer MAC header. At the egress node of Level 2, the Ethernet data packet is decapsulated to remove the outer MAC header for the present level, and is forwarded to the other PBBN on Level 1.
It can be seen from the above description of the tiered interconnection technical scheme that, it is necessary for the Ethernet data packet from Level 1 to be encapsulated with information of an outer MAC header for Level 2. That is, it is necessary for a data packet from a PBN to be encapsulated with information of two levels of MAC header, so that the number of levels of encapsulation is increased, which lowers data forwarding efficiency.
In order to avoid the lowering of the forwarding efficiency, a peer-to-peer interconnection solution can be used. With reference to FIG. 2, a schematic diagram of a peer-to-peer interconnection network is shown in FIG. 2, in which PBBN1 and PBBN2 are two provider backbone bridged networks connected in a peer-to-peer manner. In a peer-to-peer interconnection model, when a data packet enters PBBN1 through an ingress node PBB1 (Provider Backbone Bridge 1), PBB1 encapsulates the data packet with an outer MAC header. When the data packet passes through two PBBNs via PBB2 and PBB3, the Ethernet network data packet is not encapsulated with a new outer MAC header, instead, the old outer MAC header is replaced with a new outer MAC header. In order to prevent address information of specific network devices (such as PBB2 and PBB3) in the present provider Ethernet network from exposing to other provider Ethernet networks, the addresses contained in the outer MAC header used during the transmission of the data packet from PBB2 to PBB3 are usually not real addresses of the two edge nodes PBB2 and PBB3, instead are pseudo address information of PBB2 and PBB3. In that case, it needs to configure mapping relationship between respective real addresses and pseudo addresses at external network network interfaces (E-NNI) for PBB2 and PBB3, and such mapping relationship is usually configured on the basis of the I-TAG carried in a message. Then, the addresses in the outer MAC header must be translated and replaced (translated between the pseudo addresses and the real address) on PBB2 and PBB3 respectively. It can be seen that, to establish an inter-domain path between a plurality of provider Ethernet networks for data packets, it needs to perform address replacement at edge nodes, and mapping relationship must be determined to accomplish the replacement process. However, the establishment of such mapping relationship needs to be implemented by means of complex configuration when a service is established. Furthermore, since length that needs to be matched is long (at least including I-TAG, real addresses and pseudo addresses), it is difficult for the looking up of a table to be implemented by means of hardware.